n 1  :  an Old World poisonous plant of the genus Atropa (A. belladonna) having purple or green bell-shaped flowers, glossy black berries, and a root and leaves that yield atropine - called also deadly nightshade   2  :  a medicinal preparation (as atropine) extracted from the belladonna plant and containing anticholinergic alkaloids .
 
 
 
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